N. BUTRIS, R.; SHUKER JAMEEL, G. Periodic Solutions for Nonlinear System of Differential Equations of Third Order with Boundary Conditions. Journal of Education and Science, [S. l.], v. 26, n. 1, p. 126–139, 2013. DOI: 10.33899/edusj.2013.89560. Disponível em: https://edusj.uomosul.edu.iq/index.php/edusj/article/view/41376. Acesso em: 10 sep. 2025.